normal flora of human body and their functions pdf

Normal flora of human body and their functions pdf

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12.1: Normal Microbiota of the Body

Resident Flora

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Normal Microflora of Different Parts of Human Body

If your institution subscribes to this resource, and you don't have a MyAccess Profile, please contact your library's reference desk for information on how to gain access to this resource from off-campus. Please consult the latest official manual style if you have any questions regarding the format accuracy. The microorganisms that live inside and on humans now referred to as the normal microbiota are estimated to outnumber human somatic and germ cells by a factor of

12.1: Normal Microbiota of the Body

In this article we will discuss about the normal microflora of different parts of human body. An average adult human is covered with approximately 2 m 2 of skin. It has been estimated that this surface area supports about 10 12 bacteria. The skin Fig. Most skin microorganisms are associated directly or indirectly with the apocrine glands sweat glands , which are secretary glands occurring mainly in the underarm and genital regions, the nipples, and the umbilicus.

Underarm odour develops as a result of bacterial activity in the apocrine secretions. Similarly, each hair follicle is associated with a sebaceous gland, which secretes a lubricant fluid. Hair follicles provide an attractive habitat for microorganisms in the area just below the surface of the skin. The secretions of the skin glands are rich in microbial nutrients such as urea, amino acids, salts, lactic acid, and lipids.

The representative genera of microorganisms that inhabit the skin are—Acinetobacter, Enterobacter, Klebsiella, Corynebacterium, Micrococcus, Propionibacterium, Proteus, Pseudomonas, Staphylococcus, Streptococcus, Bacillus, Mycobacterium occasional , Malassezia, Pityrosporum, and Candida. The last three of the list are micro-fungi. Although the resident microflora remains somewhat constant, various factors influence its normal composition. The normal microflora of the oral cavity mouth consists of microorganisms that possess ability to resist mechanical removal and firmly adhere to surfaces like gums and teeth.

The normal microbial population able to colonize the mouth finds a very comfortable environment due to the availability of food particles and epithelial debris as nutrients, water, the suitability of pH and temperature, and the presence of many other growth factors. The oral cavity or mouth is totally free of microorganisms at the time of birth, but it is colonized by microorganisms from the surrounding environment within hours after a human baby is born.

In the beginning the microbial flora that establish in the mouth belong to the genera Streptococcus, Neisseria, Actinomyces, Veillonella, Lactobacillus, and some yeasts. These initial microorganisms are aerobes and obligate anaerobes. When the first teeth erupt, the anaerobic forms e. Later on, Streptococcus spp. The presence of these bacteria contributes to the eventual formation of dental plaques, dental caries, gingivitis inflammation of gum tissues , and periodontal disease destroy of tissue and bone.

Respiratory tract Fig. The respiratory tract consists of nose and nasopharynx, oropharynx, and throat, while the lower respiratory tract consists of trachea, bronchi, and lungs. The normal microflora of the nose occurs just inside the nostrils, and consists of staphylococci, streptococci, Neisseria, Haemophilus, etc.

Out of these S. The nasopharynx, the part of the pharynx lying above the level of the soft palate, usually contains small numbers of potentially pathogenic bacteria e. Diphtheroides occur commonly in both the nose and nasopharynx.

The oropharynx, the part of the pharynx lying between the soft palate and the upper edge of the epiglottis, contains streptococci e. The lower respiratory tract trachea, bronchi, and lungs has no resident microflora, despite the large numbers of microorganisms potentially able to reach this region during breathing.

Dust particles, which are fairly large, settle out in the upper respiratory tract. As the air passes into the lower respiratory tract, the flow rate decreases markedly, and microorganisms settle onto the walls of the passages.

The walls of the entire respiratory tract arc lined with ciliated epithelium, and the cilia, beating upward, push bacteria and other particulate matter toward the upper respiratory tract where they are then expelled in the saliva and nasal secretions.

Human gastrointestinal tract, the site of food digestion, consists of the stomach, small intestine, and large intestine. The composition of the gastrointestinal flora in humans varies considerably and is somewhat dependent on diet. For convenience, humans who consume a considerable amount of meat show higher numbers of the highly proteolytic Bacteroides and lower numbers of coliforms and lactic acid bacteria than those who consume a vegetarian diet.

Representative genera of microorganisms found in the gastrointestinal tract are shown in Fig. Many microorganisms are washed from mouth into the stomach but most of them are killed because the stomach fluids or gastric fluids are highly acidic about pH The stomach fluids therefore make the stomach a chemical barrier to entry of microorganisms into the intestinal tract.

As a result, the stomach usually contains less than to viable bacteria per millimeter of gastric fluids. The microorganisms present in stomach are mainly Helicobacter, Streptococcus, Staphylococcus, Lactobacillus, Peptostreptococcus, and yeasts e.

However, microorganisms such as Helicobater pylori may cause ulcers in susceptible human host. The small intestine is anatomically divided into three areas: the duodenum, jejunum, and ileum. The duodenum, adjacent to the stomach, is fairly acidic and contains few microorganisms gram- positive cocci and bacilli bacteria because of the combined influence of the acidic fluids of stomach and the inhibitory effect of bile and pancreatic secretions.

Lactobacilly diphtheroids, Enterococcus faecalis, and Candida albicans yeast occasionally occur in the jejulum. In ileum, the distal part of the small intestine, the pH becomes more alkaline and, as a result, anaerobic gram-negative bacteria and members of the family Enterobacteriaceae occur in it.

The large intestine or colon contains the largest number of bacterial community in human body. The large intestine or colon acts as a fermentation vessel, and the microflora of it consists primarily of anaerobic, gram-negative, nonsporing bacteria and gram-positive, spore-forming, and nonsporing bacilli.

Facultative aerobes e. The ratio of obligate anaerobes to facultative anaerobes is approximately to 1. It is because the facultative aerobes consume oxygen making the environment of the large intestine strictly anaerobic. Besides bacteria, the yeast Candida albicans and certain protozoa e. Various essential metabolic reactions are carried out by intestinal microflora and, as a result, a variety of metabolic products are formed Table Out of all vitamins produced in intestine, vitamin B 12 and K are those essential vitamins that are not made by man rather by intestinal microflora and are absorbed therefrom.

Steroids are produced in the liver and released into the intestine from gall bladder as bile acids. Steroids are modified as active steroid compounds through different metabolic processes operated in the intestine by microflora, and absorbed therefrom.

Gas flatus and odour-producing substances listed in the Table Normal human adults expel several hundred milliliters of gas from the intestines every day. Some foods metabolized by fermentative bacteria in the intestines result in the production of hydrogen H 2 and carbon dioxide CO 2. Methanogens occurring in the intestines of over one- third of normal human adults, convert H 2 and CO 2 produced by the fermentative microorganisms to methane CH 4. The uninary bladder itself is sterile in both male and female urogenital tracts, but the epithelial cells lining the urethra are colonized by gram-negative facultatively aerobic cocci and bacilli bacteria e.

The genital tract vaginal tract of an adult female, because of its large surface area and mucous secretions, possesses complex microflora. It is weakly acidic and contains significant amounts of the polysaccharide glycogen. Lactobacillus acidophilus Fig. Other microbes such as yeasts Torulopsis and Candida species , streptococci, and E.

Vaginal microflora constantly changes between puberty and the menopause. Before puberty, the female vagina is alkaline and does not produce glycogen, L. Top Menu BiologyDiscussion. Quick Notes on Microbial Pathogenicity. This is a question and answer forum for students, teachers and general visitors for exchanging articles, answers and notes.

Answer Now and help others. Answer Now. Here's how it works: Anybody can ask a question Anybody can answer The best answers are voted up and rise to the top. Mention any two carbohydrate digesting enzymes present in it.

Resident Flora

Michael, a year-old boy in generally good health, went to a birthday party on Sunday with his family. He ate many different foods but was the only one in the family to eat the undercooked hot dogs served by the hosts. His parents, assuming Michael had caught the flu, made him stay home from school and limited his activities. Growing worried, his parents finally decide to take Michael to a nearby clinic. Microbes are ubiquitous is a phrase that has been repeated often, but many people do not realize how close to home it is.

The term skin flora also commonly referred to as skin microbiota refers to the microorganisms which reside on the skin, typically human skin. Many of them are bacteria of which there are around 1, species upon human skin from nineteen phyla. Skin flora is usually non-pathogenic, and either commensal are not harmful to their host or mutualistic offer a benefit. The benefits bacteria can offer include preventing transient pathogenic organisms from colonizing the skin surface, either by competing for nutrients, secreting chemicals against them, or stimulating the skin's immune system. A major non-human skin flora is Batrachochytrium dendrobatidis , a chytrid and non-hyphal zoosporic fungus that causes chytridiomycosis , an infectious disease thought to be responsible for the decline in amphibian populations. The estimate of the number of species present on skin bacteria has been radically changed by the use of 16S ribosomal RNA to identify bacterial species present on skin samples direct from their genetic material. Previously such identification had depended upon microbiological culture upon which many varieties of bacteria did not grow and so were hidden to science.

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Skin flora : Staphylococcus epidermidis, S. Respiratory tract: Streptococcus, Corynebacterium, Haemophilus, Micrococcus,. Staphylococcus aureus is an opportunistic pathogens of skin. In normal condition S.

In this article we will discuss about the normal microflora of different parts of human body. An average adult human is covered with approximately 2 m 2 of skin. It has been estimated that this surface area supports about 10 12 bacteria.

Normal flora of human host: Types, Examples and Roles

Microbes are everywhere.

Normal Microflora of Different Parts of Human Body

Healthy people live in harmony with most of the microorganisms that establish themselves on or in colonize nonsterile parts of the body, such as the skin, nose, mouth, throat, large intestine, and vagina. The microorganisms that usually occupy a particular body site are called the resident flora. Cells of the resident flora outnumber a person's own cells 10 to 1. Microorganisms that colonize people for hours to weeks but do not establish themselves permanently are called transient flora. The resident flora at each site includes several different types of microorganisms. Some sites are normally colonized by several hundred different types of microorganisms.

 Прошу начальника систем безопасности связаться с главным коммутатором, где его ждет важное сообщение. От изумления у Джаббы глаза вылезли на лоб. Похоже, она от меня не отвяжется. И он решил не реагировать на сообщение. ГЛАВА 79 Стратмор спрятал пейджер в карман и, посмотрев в сторону Третьего узла, протянул руку, чтобы вести Сьюзан за. - Пошли.

Он предоставил АНБ выбор: либо рассказать миру о ТРАНСТЕКСТЕ, либо лишиться главного банка данных.

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Наверное, он сейчас у. - Понимаю.  - В голосе звонившего по-прежнему чувствовалась нерешительность.  - Ну, тогда… надеюсь, хлопот не. - Отлично. Он обедает там сегодня с одной из наших сопровождающих.  - Ролдан понимал, что сейчас они скорее всего лежат в постели, но ему не хотелось оскорблять чувства звонившего.

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